Acetabular reaming systems are well known in hip arthroplasty, to prepare bone tissue for receiving a hemispherical implant U.S. Pat. No. 5,658,290 to one of the present inventors, the entire contents of which are expressly incorporated by reference herein and relied-upon, discloses such a system. In the afore-mentioned patent, a surgical driver includes a quick disconnect mechanism having catches that receive a pair of orthogonal bars from a domed cutting tool.
It is highly desirable that the bone is shaped by the rotary tool into a cavity that conforms closely in hemispherical shape and dimension to the implant being received. Those skilled in the art have sought to provide rotary cutting tools that form the bone into a precise hemispherical cavity. It is further desirable to advance the tool linearly into the bone to fully cut the cavity, versus having to rock the tool sideways by changing its orientation to achieve a complete shape.
For example, one system has a tool with a cylindrical rim that continues parallel past the hemispherical equator of the tool, in order to allow presentation of teeth for a full cut. Such prior domed tools are referred to as “high-rim” reamers. Although these high-rim reamers have teeth presented for a straight-in (linear) advancement of cut into the cavity, there is no visual confirmation guiding the user to the finished cut. Actual position of the outer equatorial edge of the tool in the bone cavity is obscured and the user does not know exactly when to stop pushing in the tool.
Another type of tool is found in what is known as “hemispherical” reaming systems. These tools have no teeth presented for a full cut of the cavity simply by linear advancement of the tool into the bone. That is, a full, a straight-in cut is not possible hence the tool must be rocked sideways in order to present the teeth for cutting the final shape. This may result in over-cutting of the cavity.
Accordingly, a need exists for an improved reaming system wherein the user may precisely ascertain the swath being cut by the tool as it bottoms-out in the bone, to completely form the hemispherical-shaped cavity without the risk of over-cutting. Particularly, there is a need for visual confirmation by the user of the position of the equatorial edge of the tool as the cavity is being fully cut.
There is also a need for an improved. reaming system wherein the tool is linearly advanced without having to “rock” the tool by changing the orientation of the cutting approach, in order to achieve a full cut.
There is a further need for a rotary cutting tool having a tooth design that precisely cuts a cavity with the desired size and shape of an implant to be received in the cavity, while employing a linear cut guided by accurate visual confirmation by the user.